Mpemba Effect

THE MPEMBA EFFECT by Laura Dahl and Madeline Graham
Abstract:

MPEMBA EFFECT. Maddeline Graham and Laura Dahl. The purpose of this lab was to attempt to recreate the Mpemba effect and isolate some of the factors involved. The Mpemba effect occurs when two equal volumes of water, one hotter than the other, are placed in a subzero environment and the relatively hotter quantity freezes first. The variables tested were container material (conductive metal v. insulating plastic), open versus closed system and, in a separate part of the experiment, volume. It was concluded that the Mpemba effect was not achieved in any of the trials, that container material did not significantly affect the freezing rate of the water, and that whether the system was open or closed had a negligible effect of the freezing rate. The variables were chosen based on the principles surrounding the Mpemba effect including thermodynamics, thermochemistry, and properties of freezing water such as supercooling and the difference between reaching the freezing temperature and actually freezing the water completely. In addition, the open versus closed trials of the experiment was designed to isolate the effect of evaporative cooling, cooling in which relatively fast-moving, hot water molecules on the surface leave, removing heat energy from the body of water. This experiment examined the rates of cooling to 0°C of the various volumes of water with one of two initial temperatures, 21°C or 100°C. Despite the predicted outcome, a successful reproduction of the Mpemba Effect, the initially 21°C water consistently reached 0°C before the initially 100°C water. The Mpemba effect could be effectively applied to any operation which requires the rapid freezing of water or in planning the infrastructure of buildings so as to prevent pipes from bursting in cold weather.Keywords: supercooling, Mpemba effect, thermodynamics, evaporative cooling, thermochemistry, freezing point

Figure 1: Freezer, LoggerPro, laptop, open plastic and metal containers, temperature probe setup

Figure 2: Phase Two Walk-In Freezer Set Up

Figure 3: Summary Graph of Freezing Times: by Container Type

Figure 4: Summary Figure of Freezing Times: by System Type

Mpemba Recording:
Mpemba Effect.wav


Works Cited

Brownridge, J. D.(2011). When does hot water freeze faster then cold water? A search for the Mpemba effect. American Journal Of Physics, 79(1), 78-84. doi:10.1119/1.3490015

Monwhea, J. (2006). The Mpemba effect: When can hot water freeze faster than cold?. American Journal Of Physics, 74(6), 514-522. doi:10.1119/1.2186331

Katz, J. I. (2009). When hot water freezes before cold. American Journal Of Physics, 77(1), 27-29. doi:10.1119/1.2996187